Efforts directed at improving air quality and increasing energy production from renewable resources have resulted in renewed interest in alternative fuels, such as ethanol and butanol, that might replace gasoline and diesel fuel, or be used as additives in gasoline and diesel fuel.
It is known that 1-butanol can be prepared by condensation from ethanol over basic catalysts at high temperature using the so-called “Guerbet Reaction.” See for example, J. Logsdon in Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley and Sons, Inc., New York, 2001.
Methods of using catalysts to convert ethanol to butanol are also discussed in the following references.
M. N. Dvornikoff and M. W. Farrar, J. of Organic Chemistry (1957), 11, 540-542, disclose the use of MgO—K2CO3—CuCrO2 catalyst system to promote ethanol condensation to higher alcohols, including 1-butanol. The disclosed liquid phase reaction using this catalyst showed a 13% conversion of ethanol and 47% selectivity to 1-butanol.
U.S. Pat. No. 5,300,695, assigned to Amoco Corp., discloses processes in which an alcohol having X carbon atoms is reacted over an L-type zeolite catalyst to produce a higher molecular weight alcohol. In some embodiments, a first alcohol having X carbon atoms is condensed with a second alcohol having Y carbon atoms to produce an alcohol having X+Y carbons. In one specific embodiment, ethanol is used to produce butanol using a potassium L-type zeolite.
J. I. DiCosimo, et al., in Journal of Catalysis (2000), 190(2), 261-275, describe the effect of composition and surface properties on alcohol-coupling reactions using MgyAlOx catalysts for alcohol reactions, including ethanol. Also condensation reactions on MgyAlOx samples involved the formation of products containing a new C—C bond, such as n-C4H8O (or n-C4H9OH) and iso-C4H8O (or iso-C4H9OH). They also describe, in Journal of Catalysis (1998), 178(2), 499-510, that the oxidation to acetaldehyde and the aldol condensation to n-butanol both involve initial surface ethoxide formation on a Lewis acid-strong base pair.
WO 2006059729 (assigned to Kabushiki Kaisha Sangi) describes a process for efficiently producing, from ethanol as a raw material, higher molecular weight alcohols having an even number of carbon atoms, such as 1-butanol, hexanol and the like. The higher molecular weight alcohols are yielded from ethanol as a starting material with the aid of a calcium phosphate compound, e.g., hydroxyapatite Ca10(PO4)6(OH)2, tricalcium phosphate Ca3(PO4)2, calcium monohydrogen phosphate CaHPO4×(0-2)H2O, calcium diphosphate Ca2P2O7, octacalcium phosphate Ca8H2(PO4)6×5H2O, tetracalcium phosphate Ca4(PO4)2O, or amorphous calcium phosphate Ca3(PO4)2×nH2O, preferably hydroxyapatite, as a catalyst, the contact time being 0.4 second or longer.
Carlini et al. describe a catalytic reaction of methanol with n-propanol to produce isobutyl alcohol. The involved catalyst is a calcined hydrotalcite in combination with copper chromite. See C. Carlini et al, Journal of Molecular Catalysis A: Chemical (2005), 232 (1-2) 13-20. See also C. Carlini, Journal of Molecular Catalysis A: Chemical (2004), 220 (2), 215-220, in which the catalyst is a mixture of a hydrotalcite with Pd, Ni, Rh, or Cu, with the mixture being calcined at 500° C.
Hydrotalcites are layered, double hydroxides of the general formula(M2+1−xM3+x(OH)2)(An−x/n).yH2OThe M2+ ions can be a variety of divalent cations (e.g., Mg, Ni, Pt, Pd, Zn, Co, Fe, Cu) and the M3+ ions can be trivalent Al, Fe or Cr. Some hydrotalcites are described by V. K. Diez, C. R. Apesteguia, and J. I. DiCosimo (Latin American Applied Research, 33, 79-86 (2003)) and N. N. Das and S. C. Srivastava (Bull. Mater. Sci. 25, (4), 283-289 (2002)).
It has been found that partially or fully thermally decomposed hydrotalcites, particularly those that incorporate transition metals, are catalysts that are effective for the conversion of ethanol to a reaction product that comprises (i.e., contains, among other things) 1-butanol.